A single-lever tub and shower faucet is a basic plumbing project and does not require hiring a plumber. Single-lever faucets do not have as many parts and pieces as two-handle faucets, making the task less difficult. Newer faucets have even fewer pieces than their old-fashioned counterparts; older faucets use washers whereas newer faucets have a cartridge that allows for a less tedious installation.
Turn off the main water supply to the house; the shut-off is usually in the basement or near the water meter.
Turn a faucet on to drain water from the pipes.
Place the faucet cartridge over the valve, seated just inside the wall if the wall is finished. If this is new construction, it is the valve seated in a straight line with the faucet hole on the tub, in between two studs.
Attach the clip with needle-nosed pliers onto the cartridge and valve to hold it in place.
Place the metal sleeve that came with the faucet over the cartridge and press it back toward the wall as far as possible. Do not push it forcefully, just guide it in gently.
Place the escutcheon, which is decorative back plate, in place and screw in to the wall. The number of screws depends on the brand of faucet.
Slip the faucet handle over the valve and secure in place with a screw. The screw comes with a new faucet assembly.
Press the handle cover in place. It is usually made of plastic and snaps on to hide the screw.
Turn the water on at the main valve.